1. Technical Field
The present invention relates to a valve assembly and associated methods for use in wellbore, downhole or intervention operations, such as for subsea wellbore operations. In particular, but not exclusively, the invention relates to a connection between a subsea riser and a subsea wellhead.
2. Background Information
Subsea operations often involve the connection of a surface vessel or platform to a subsea wellhead via a riser. Safety valves having a shearing arrangement are commonly used to cut objects such as wireline, slickline, coiled tubing, tooling and/or the like which may extend through the riser to the wellhead during subsea operations and to isolate the riser from the wellhead in an emergency. For example, Blow-out Preventers (BOP) are commonly installed as part of permanent infrastructure which is located at a subsea wellhead. BOP's typically have rams with cutting plates to shear objects such as wireline, slickline, coiled tubing, tooling and/or the like which extends through the riser.
For a lightweight subsea riser, for example for use with lightweight intervention tooling, there may be no permanent subsea safety valve. Instead, a well control package may be connected in the riser tubing string, wherein the well control package comprises a valve assembly for cutting the wireline, slickline, coiled tubing, tooling and/or the like and for sealing the riser from the wellhead to prevent fluid flow from the wellhead to the riser.
Ball valve assemblies are known which comprise first and second conduits and a ball valve member having a through-hole foamed therein, wherein the ball valve member is mounted between respective ends of the first and second conduits for rotation about a valve member rotational axis between an open position in which the through-hole of the ball valve member is aligned with the ends of the first and second conduits and a closed position in which the ball valve member is misaligned with the ends of the first and second conduits and creates a seal therebetween. Such ball valve assemblies may be configured to shear wireline, slickline, coiled tubing, tooling and/or the like extending through the first and second conduits and the valve member through-hole as the ball valve member is rotated towards the closed position. For example, U.S. Pat. No. 3,971,438, incorporated herein by reference, discloses a tubular housing and a ball valve assembly housed within the housing, the ball valve assembly comprising a ball valve member having slots which are eccentrically located with respect to a rotational axis of the ball valve member. A hydraulically actuated annular piston is located around the ball valve member. Pins extend radially with respect to a longitudinal axis of the valve assembly between the ball valve member and the annular piston. In operation, the piston is hydraulically actuated along the longitudinal axis and a force is transferred between the piston and the ball valve member through the pin and slot arrangements for rotation of the ball valve member.
This background serves only to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the invention may or may not address one or more of the background issues.